Pilot valve



April 23, 1935. 1 AMAXSON I 1,998,553

PILOT VALVE Filed Dec. 30, 1929 Kiwi Patented Apr. 23, 1.935

* UNITED STATES PILOT VALVE Louis A. Maxson, Claremont, N. H.', assignorto Sullivan Machinery Company, a corporation of MassachusettsApplication December 30, 1929, Serial No. 417,275

14 Claims.

This invention relates to fluid controlling mechanisms, and moreparticularly to a pilot valvemechanism for controlling the loadingand/or unloading, for instance, of a compressor.

One'object of my invention is to provide an improved fluid pressurecontrolling device, and more specifically, a device which will permitrelatively close regulation without the usual difiiculties attendantthereto, such as fluttering of the valve member, small differentialareas, etc.

A further object is to accomplish this close regulation by operatingcertain of the parts with forces; whether fluid pressure or otherwise,of such magnitudethat the movable elements will be positively controlledand yet will permit a satisfactory degreeof regulation betweenrelatively close pressure limits, thereby permitting the parts to bemanufactured without that degreeof precision and nicety which has beennecessary in prior attempts to obtain close regulation. A further andmore specific object of my invention is to reduce the range of the pilotvalve operating forces which without my improved means would be present,and thus obtain a close pressure regulation. Other objects andadvantages of my invention will be apparent from the followingdescription.

In thea ccompanying drawing I have shown one form which my invention mayassume in 0 practice.

In this drawing,

Fig. 1 is a vertical'section of the pilot valve control mechanism.

Fig. 2 is a transverse section thereof taken on 5 line 2-2 of Fig. 1.

While my; invention is specifically shown as a pilot valve most suitablefor controlling the loading and unloading of, say, a compressor, it willof coursebe understood that the same may have 4 variousapplicationswherein it is desired to control the pressure in, for instance, anyreceptacle or pipe line which is supplied from a suitable source offluid pressure and which source would in turnbe controlled bymy'improved mechanism. r e

- In the illustrative embodiment thereof, my improved arrangementcomprises a diaphragm I clamped between a cylinder 2 and a lower casing.3 to form a pressure chamber 4, to which fluid pressure is supplied,through a suitable connection. 5 leading from the air receiver, pipeline, or other pressure fluid containing means, and from whichfluidpressure may be supplied through a suitable connection 6 to the meansfor controlling the source of pressure for the receiver.

In the particular. embodiment, fluid pressure may be supplied throughthe connection 6 to either an intake,.inlet, or exhaust valve typeofcompressorunloading mechanism to unload the compressor, and the fluidthussupplied is exhausted through the connection 6 when the compressoris loaded, these operations being usual and well understood. The pilotvalve for thus controlling the flow of fluid from the chamber 4 and theventing of fluid from the connection 6 is specifically shown as of thewell known Judson type, which, briefly, consists. of a movable hollowvalve stem 1 adapted to be closed at its lower end by a perforatedflanged disc 8 by the action of a spring 9 holding the members inengagement when the diaphragm I is in its lowermost position. Duringthis position, which is had when the receiver pressure is below apredetermined minimum, the connection 6 will be vented through passagesI0 suitably connected with the chamber in which the valve member 8 isdisposed. On the other hand, when the receiver pressure has reached apredetermined maximum so that the diaphragm I is moved upwardly bypressure in chamber 4, the valve stem I likewise will move upwardly awayfrom disc 8 when the latterengages an annular seat II disposed outsideof the perforations in the disc 8, whereupon fluid pressure mayflow'from the chamber 4 through suitable openings in the. valve stem Iand the perforations in disc 8 through the connection 6 to the unloadingor other controlling mechanisms. During this time communication of thevent passages ID with the disc chamber is closed, while an auxiliaryspring I2 holds stem I away from disc 8.

.The means for pressing the diaphragm towards loading position comprisesa spring I3'interposed between a suitable disc resting against thediaphragm and a collar I 4 which is slidably mounted or guided within acylindrical extension I5 of a closure member I 6 suitably clamped withthe diaphragm I between the cylinder 2 and casing 3. A second spring II,placed in series with spring I3, is held between a removable cover I8and a piston I 9, which in turn bears upon a small projection on disc I4through an adjustable screw 20. Any suitablemeans may be provided toprevent rotation of piston I9 while screw 26 isbeing adjusted, e. g. asplineway and spline, a guide rod, or the like.

The piston I9 comprises a head plate removably attached to an annularbody, 2|, the bore of which slidably receives the cylindrical extensionI5, while a suitable annular flexible cup packing 22 prevents leakagewhen pressure is supplied to chamber 23 from the receiver conection 5,as by a passage 24. Any leakage that might occur past the packing andinto the inner piston chamber is vented to the atmosphere through ports25 and 26.

Be it assumed that the receiver pressure is below the desired minimumvalue. The parts will then be in the position shown, in which diaphragmi and pilot valve stem I are in their lowest position, thus causingventing of connection 6 to atmosphere, thereby causing loading of thecompressor or causing any other source of supply to replenish, ordeliver fluid to, the receiver. While receiver pressure is building upto a predetermined maximum it acts on the lower sides of diaphragm l andalso upon piston 19. The piston will thus gradually be moved andcompress spring ll, thereby relieving the tension of spring l3 by anamount which will permit the diaphragm l to be moved upwardly far enoughto effect loading, by a unit pressure in diaphragm chamber 4 less thanthat which would be required if the force of spring I3 were not variedby the intervention of the force on piston I9. The upward movement ofdiaphragm i is accompanied by a corresponding movement of valve stem Iand pilot valve disc 8, until the-latter engages seat ll, after whichfurther upward movement of stem 1 permits fluid pressure to flow fromchamber 4 through the connection E to operate the unloading mechanismand thus unload the compressor. The pressures exerted by springs l3 andll must, of course, be adjusted to permit each to yield suitably duringthe period between loading and unloading.

It will be noted that were the abutment l4 stationary at all times,there would be required say n units of pressure increase to move thediaphragm from loading to unloading position. Because upward movement ofpiston 2| occurs too while the diaphragm l is being pressed upwardly,less than n units of pressure increase in chamber 4 will permitunloading. Therefore a closer regulation is obtained.

While I have in this application specifically described one form whichmy invention may assume in practice, it will be understood that thisform of the same is shown for purposes of illustration and that theinvention may be modified and embodied in various other forms withoutdeparting from its spirit or the scope of the appended claims.

VJhat I claim as new and desire to secure by Letters Patent is:

1. A fluid pressure controlling device comprising a valve mechanism,means for forming a fluid pressure chamber including a movable fluidpressure operated element forming in all positions thereof a Wall ofsaid chamber and cooperating with said valve mechanism to move the same,said chamber having communication with the pressure to be controlledirrespective of the position of the valve mechanism, means for holdingsaid fluid operated element and valve mechanism in one direction by apredetermined force, and means auto matically operative during pressurevariations on said element and governed by pressure which rises andfalls simultaneously with the pressure in said chamber for varying theforce with which said valve mechanism is held whereby the upper limit ofpressure regulation of the pressure within said chamber is of lowervalue than would be obtained by said holding means acting alone.

2. A fluid pressure controlling device comprising a movable element,structurally distinct, fluid pressure actuated means for moving the samein one direction, means for moving the same in the opposite directionincluding a plurality of yieldable elements placed in series with eachother and having similar ranges of yielding and each increasinglystressed on movement of said element in the first direction, and meansinterposed between said elements whereby the force normally transmittedfrom one to the other may be varied.

3. The combination set forth in claim 2 further characterized by theprovision of means interposed between said series elements for adjustingthe force of said elements.

4. A fluid pressure controlling device comprising a casing, a diaphragmassociated therewith to form a fluid pressure chamber, a pilot valveunloading mechanism associated with said diaphragm and moved in onedirection in accordance with the fluid pressure in said chamber, andmeans for moving said diaphragm in the opposite direction including apair of springs placed substantially in axial alinement, a pistoninterposed between the adjacent ends of said springs, and means forsupplying fluid pressure to said piston whereby said diaphragm may bemoved in a. direction against said springs with a force less than thatcreated by said springs without the action of said piston.

5'. A pilot valve unloading mechanism comprising a casing, a diaphragmdisposed therein for forming a closed fluid pressure chamber to whichfluid pressure is supplied from a suitable source of pressure to becontrolled, a valve mechanism controlled by said diaphragm and adaptedto permit flow of fluid from said chamber to permit control of thesource, a pair of springs acting together to hold said diaphragm andvalve mechanism in one position, a fluid operated piston associated withsaid springs, and means for operating said piston by fluid pressuresupplied from said source whereby upon a. predetermined maximum fluidpressure said piston is moved substantially simultaneously with movementof said diaphragm to vary the spring force acting upon said diaphragm. V

6. A pilot valve mechanism comprising a casing having a cylindricalbore, a diaphragm disposed therein transversely of one end of said boreto provide a fluid pressure chamber, a pilot valve mechanism controlledby said diaphragm and having a passage adapted to be connected tounloading mechanism, an enclosure member disposed within said casingbore and having a cylindrical extension, a piston also disposed withinsaid bore and slidably engaging the walls thereof and being providedwith a bore with which said cylindrical extension has slidabletelescopic engagement, controlling means associated with said pistonincluding a spring interposed between said diaphragm and the end of saidpiston. and means for supplying fluid pressure to said diaphragm chamberand one side of said piston.

'7. The combination set forth in claim 6 further characterized in thatsaid means which is associated with the piston also includes a springinterposed between said piston and the end of said casing opposite tothat in which said diaphragm is disposed.

8. The combination set forth in claim 6 further characterized in thatthe fluid pressure for said diaphragm chamber and piston is suppliedfrom a common source.

9. The combination set forth in claim 6 further characterized in thatsaid spring which is interposed between said diaphragm and the piston is12. In a pump pilot valve mechanism, a valve disposed within saidenclosure element while the interior of the latter and the bore of saidpiston are vented to atmosphere.

10. An unloading pilot valve control comprising a casing having acylindrical bore, a diaphragm disposed therein transversely of one endof said bore to provide a fluid pressure chamber, a pilot valvemechanism controlled by said diaphragm and having a passage adapted tobe connected to unloading mechanism, an enclosure member disposed withinsaid casing bore and having a cylindrical extension, a piston alsodisposed within said bore and slidably engaging the walls thereof andbeing provided with a bore in which said cylindrical extension istelescopically arranged, said piston having a portion extending acrossits bore, means associated with said piston including a springinterposedbetween said piston portion'and said diaphragm, means forsupplying fluid pressure to said diaphragm chamber and one side of saidpiston, and a second spring interposed between said piston portion andthe end of said casing opposite to that of said diaphragm,

11. A pilot valve control comprising a casing having a cylindricalbore,a diaphragm disposed therein transversely of one end of said boreto provide a fluid pressure chamber, a pilot valve mechanism controlledby said diaphragm and having a passage adapted to be connected tounloading mechanism, an enclosure member disposed within said casingbore and having an extension, a piston also disposed within said boreand slidably engaging the walls thereof and being provided with a borein which said cylindrical extension is telescopically arranged, saidpiston having a head extending across its bore, means associated withsaid piston including a spring interposed between said head anddiaphragm, a second spring interposed between said piston head and theend of said casing opposite to that of said diaphragm, and means forsupplying to said diaphragm chamber and one side of said piston fluidpressure which is to be regulated while the other side of said piston issubjected tov constant fluid pressure.

movable to control loading and unloading, and controlling means thereforincluding coaxial pump discharge pressure pressed members and seriallyacting resilient means respectively compressed by movement in the samedirection of each of said members.

13. In a valve mechanism, a controlling valve and means for regulatingthe position .of said valve substantially exclusively in accordance withthe pressure at the supply side of said valve whereby said valve mayupon the attainment of a predetermined pressure at the supply sidethereof effect substantial equalization of pressure at its oppositesides, said regulating means including a member movable by supply sidepressure and means for controlling movement of said member by saidpressure including yielding means opposing said movement, a yieldingabutment against which said yielding means reacts in opposing suchmovement, and means subjected to a pressure which bears a constantrelation to the supply pressure for varying the resistance opposed bysaid yielding abutment.

14. In a valve mechanism, a controlling valve and means for regulatingthe position of said valve substantially exclusively in accordance withthe pressure at the supply side of said valve whereby said valve mayupon the attainment of a predetermined pressure at the supply sidethereof efiect substantial equalization of pressure at its oppositesides, said regulating means including a member movable by supply sidepressure and means for controlling movement of said member by saidpressure. including yielding means opposing said movement, an abutmentagainst which said yielding means reacts in opposing such movement,yielding means against which said abutment reacts during the opposing ofsuch movement, andmeans subjected to a pressure which bears a constantrelation to the supply pressure acting in opposition to the resistanceoilered by said second mentioned yielding means.

LOUIS A. MAXSON.

